The present invention relates to devices for injecting, delivering, infusing, dispensing or administering a substance, and to methods of making and using such devices. More particularly, it relates to a needle guard device which is or can be attached to an injection device of a type which may be used for administering or self-administering medicaments, for example insulin. The injection device may be a simple syringe or a syringe which is disposed of once it has been used. In such applications, the needle guard may be manufactured separately from the injection device and connected to the injection device in readiness for administering, or it may be an integrated part of the injection device and be disposed of with it. The injection device may be designed for repeated use and to enable a dose to be set or selected for the product to be administered. In some embodiments, the injection device may be an injection pen of the type used to treat diabetes and, these days, for other treatments as well.
When handling injection devices, there is a risk that patients or medical staff could be injured by an injection needle and/or be infected by an accidental stick by an injection needle that has already been used. With a view to preventing this, needle guard devices with a displaceable needle guard have been developed. For the injection, the injection device fitted with the needle guard device is pushed against the skin via the needle guard. Due to the pressure, the injection device, with the injection needle projecting from it in the distal (forward, front or injection) direction, moves in the distal direction relative to the needle guard so that the injection needle pierces the skin. Accordingly, the needle guard effects a movement in the proximal direction (rearwardly) relative to the injection device as far as a releasing position in which the injection needle projects in the distal direction beyond the needle guard by its injection portion which pierces the skin. When the injection needle is pulled back out of the skin, the needle guard is subjected to an elastic force of a rebounding element and moves in the distal direction again as far as a guard position in which it extends beyond the injection needle, including the needle tip. On reaching the guard position, the needle guard locks automatically so that it can not move back in the proximal direction relative to the injection needle again.
Such needle guard devices are known from U.S. Pat. No. 6,773,415 B2 and WO 01/91837 A1. At the end of its retracting movement, the needle guard moves into an irreversible lock, as a result of which the needle guard is no longer able to move in the distal direction into the initial position and can only move into the guard position when left to its own devices, i.e. when relived of the external force.